1. Field of the Invention
This invention relates to a method of tagging a substance to allow subsequent or retrospective identification thereof. More specifically, this invention relates to the use of polypeptides as tagging materials.
2. Description of the Prior Art
The inclusion of a material in a source substance or composition for subsequent or retrospective identification of such substance or composition is well known in the art. Such a method is usually referred to as "tagging". For example, it is known to include a tagging material in explosives in order to permit the identification thereof after detonation. As another example, it is known to measure the flow of water in a river by injecting a tagging material (e.g. dye) into the river and determine the concentration of the tagging material at a location downstream from the injection point. As a further example, the spreading of an oil spill can be determined by tagging the oil with a suitable material. Thus, tagging materials represent an extremely useful tool in scientific research, environmental protection, law enforcement and other fields.
In general, the tagging material used must be inert and readily identifiable with accuracy. Known tagging materials include radioactive isotopes, magnetically coded particles and multi-layer paint chips. However, radioactive isotopes must be handled with care and are usually expensive. On the other hand, magnetically coded particles and paint chips cannot be readily identified with accuracy. This is due to the fact that the amount of the tagging material present in the substance in the subsequent identification step may be extremely small, making determination thereof difficult. Thus, there exists a need for a tagging material which causes little or no harm to the environment and can be readily and easily identified at a high accuracy.